Edward Another method to get information on oxidation states from near-edges was used relatively commonly in the 1980s and early 1990s, but has gone out of fashion since (can someone tell me why? Is the underlying physics flawed?). You determine the ionisation potential (IP) by fitting the arctan step background function simultaneously with Gauss/Lorentz lines for all the near-edge resonances. The inflection point of the arctan corresponds to the IP. Variations in the IP can be interpreted using the same considerations as for binding energy shifts in XPS... For example, for Au there is an almost perfectly linear relationship between IP and oxidation state, from Au(-1) via Au(0) and Au(+1) to Au(+3) ! In this case the correlation with oxidation state is a lot stronger than for white line intensities and/or the now commonly used 'edge inflection points'... Sven -- Sven L.M. Schroeder (mailto:s.schroeder@manchester.ac.uk) School of Chemical Engineering and Analytical Science (CEAS) & School of Chemistry The University of Manchester PO Box 88 Sackville Street Manchester M60 1QD United Kingdom http://www.slmslab.info Tel +44 (161) 306 4502 Lab +44 (161) 306 4486 Fax +44 (161) 306 4399 Offices: School of CEAS: Room C17 (Jackson's Mill) School of Chemistry: Room E3 (Faraday Undergraduate Block) DISCLAIMER The views expressed within this message are those of the sender, not those of The University of Manchester or one of its Departments. While all emails and attachments are scanned for viruses before sending, we cannot accept any responsibility for viruses, so please scan all emails and attachments. This email is intended for the addressee only. If you are not the intended recipient, please notify the sender and delete this email immediately. END OF MESSAGE
-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Bruce Ravel Sent: 17 May 2007 21:36 To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] white line intensity v. edge position in determiningoxidation state of Re
I am trying to determine the oxidation state of Re in PtRe nanoparticles catalysts supported on carbon. The ReLIII edge was measured before and after an in-situ reduction in hydrogen. Can anyone suggest Which characteristic of the edge is more related to oxidation state ? Is it the integrated white-line intensity or the
the edge(point of maximum derivative). The edge position of
On Thursday 17 May 2007, Edward L. Kunkes wrote: position of the ReLIII
edge of my particles is the same as that of Re foil, however the white line instensity is significanty higher. For the non-reduced PtRe particles, the edge position is similar to that of ReO2 (with a larger white line intensity).
I see that no one has responded to this, so I'll take a stab.
Presumably you know what the end members -- Re metal and Re oxide -- look like. Can you do linear combination fitting of the intermediate spectra to determine the average oxidation?
B
-- Bruce Ravel ---------------------------------------------- bravel@anl.gov
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